The improving economics of deploying solar arrays is making it attractive for facility owners and/or operators of assets such as rooftops, reservoirs, landfills and brownfields to deploy commercial-scale photovoltaic (PV) solar panel systems on these assets. In landfill and brownfield applications, deploying solar arrays directly to exposed geomembrane caps (EGC's) provides additional savings due to the elimination of costs associated with installation and maintenance of a two (2) foot vegetative layer required on traditional landfills. Referring to FIG. 1, a conventional grass-topped landfill cover system is shown on the right. The geomembrane cap is indicated at 10. Beneath the geomebrane 10 is waste, an intermediate cover layer and a final grading layer. Grass-topped cover systems require additional layers of drainage media, support soil, top soil, and grass on top of the geomembrane 10. Maintenance of the grass on top is a continuing expense.
On the left of FIG. 1, is an EGC system including a flexible solar panel 12 adhered directly to the surface of the geomembrane 10. The deployment of solar covers such as these require geomembrane materials that can remain exposed to the elements for years and serve as a substrate for adhering flexible photovoltaic panels. In these cover systems, the exposed geomembrane is anchored directly into the landfill and the solar panels are adhered directly to the surface of the membrane. It can be appreciated from the side-by-side figures that the elimination of the grass, top soil and vegetative soil layers will significantly increase the amount of waste that can be accumulated for closing the landfill. Conventional solar arrays using rigid glass-encapsulated panels on metal frames with concrete bases, are less desirable because of the weight of these systems on the landfills. The weight and requisite rigidity of conventional array systems combined with the differential settlement of the underlying waste, causes movement of the arrays which can cause breakage of panels. Over the course of a 20 year deployment, the waste material beneath the cover will settle significantly and cause movement of both the membrane and the photovoltaic panels.
Accordingly, the prior art methods of deploying solar panels on exposed membranes have focused on using flexible panels (See FIGS. 1 and 2) and directly adhering the flexible panels 12 to the surface of the geomembrane 10 using adhesive backing. The flexible geomembrane 10 and flexible panels 12 were thought to be better suited to provide for settling of the waste material over time. Flexibility and movement of the panels is critical to long-term deployment.
Initial attempts at adhering the panels directly to the membrane have had some success. There are several deployed systems that are currently in operation across the country. However, there are also obvious drawbacks to adhering the panels directly to the membrane. A major drawback that has been encountered is maintenance of the panels and geomembranes, and repair or replacement of panels should they be defective or become damaged. While the panels are engineered to withstand the elements, there is still significant risk that the panels will become damaged over a lengthy period of time and will need to be replaced. Even though the panels are flexible, settlement of the waste material results in movement of the membrane and places tremendous stress on the adhered panels causing failures of the adhesive and requiring re-adhering of the panels or panel replacement. In addition, there are known issues with the adhered panels tearing the membranes due to thermal expansion where the adhesive constrains movement of the geomembrane. The coefficient of thermal expansion of the panels is different than that of the membrane. At both high and low temperatures, expansion or contraction of the panels relative to the membrane causes shearing stress on the adhesive layer and can result in failure of the panel, geomembrane and/or adhesive layer.
Another drawback is the inability to redeploy the solar array in the event the facility should require its removal for any reason. This is not possible when the panels are adhered directly to the membrane. For example, certain landfill operators plan and develop their facilities in stages that require shorter term deployment than the economics of a permanent adhesive attachment system can provide. A solar array that can be easily removed and redeployed would allow operators to attach to an EGC on a short term basis, and then remove and redeploy the array at a different location. This is not feasible when the panels are adhered directly to the membrane.
By way of providing additional background, context, and to further satisfy the written description requirements of 35 U.S.C. § 112, the following references are incorporated by reference in their entireties: U.S. Pat. Nos. 4,249,514; 6,672,018; 7,406,800; 8,919,052; 8,316,590; 8,240,109; 8,256,169; 8,418,983; 4,321,745; 61,595,370; US Pat. Publ. Nos.: 2011/0284058; 2011/0072631 2013/0200234, 2015/0153394; 2014/0127935; 2014/0032178; 2014/0025344; 2014/0025220; 2014/0025215; 2014/0020244; 2014/0020230; 2014/0000916; 2013/0262040; 2013/0061198; 2013/0061189; 2013/0061142; 2012/0323635; 2011/0173110; 2011/0137752; 2010/0170163; 2015/0200618; 2014/0326838; 2014/0251431; 2014/0246549; 2014/0223838; 2014/0182662; 2014/0175244; 2014/0174511; 2014/0158184; 2014/0130847; 2014/0102997; 2014/0053891; 2014/0026946; 2013/0183084; 2013/0180574; 2013/0180573; 2013/0180572; 2013/0140416; 2013/0133270; 2012/0298188; 2012/0298186; 2012/0279558; 2012/0260972; 2012/0255598; 2012/0125410; 2008/0234421; 2010/0236183; 2009/0250580; 2011/0047903; 2010/0192505; and 2011/0162779.